The etiological agent responsible for the most severe form of human malaria is the intraerythrocytic protozoan parasite Plasmodium falciparum. Clinical manifestations of P. falciparum malaria include cerebral malaria, which is the major cause of death from this disease, whereby infected erythrocytes sequester in the deep vascular beds of the brain. During growth of the asexual stage of the parasite in human erythrocytes, a series of extensive changes occur in the structural and functional properties of the infected erythrocyte, includes the development of knob structures and the ability to adhere to endothelium. Crucial to these changes are proteins of parasite origin, which are either deposited on the inner aspect of the erythrocyte membrane or inserted into it. Several parasite proteins are present at the cytoplasmic side of the knob structure including the knob-associated histidine rich protein (KAHRP), PfEMP3, MESA and FIRA. The adhesive properties of P. falciparum infected red cells are due to the antigenically variant parasite protein PfEMP1 which is concentrated in the knob on the outside of the membrane. It is likely that interaction of the cytoplasmic tail of PfEMP1 with other proteins and the cytoskeleton of the red blood cell as well as the membrane mechanical properties are crucial to the strength of the adhesive interactions of the parasite-infected red cell with ligands on endothelial cells. The hypotheses to be tested, in this work, are that KAHRP, PfEMP3, MESA and FIRA are important for the expression of the adhesive properties encoded by PfEMP1 on the P. falciparum infected red cell surface and/or the membrane mechanical properties of the infected erythrocyte. This will be done by constructing targeted gene disruptions of these genes either singly or as double knockouts as well as introducing mutated genes to determine the effect on the adhesive and membrane properties of the parasite-infected red cell. This will enable an understanding of the role of these proteins in determining the adhesive properties of the infected red cell and/or the membrane mechanical properties. Additionally we will use green fluorescent protein fused to KAHRP to analyze the trafficking of this protein as well as the functional role of the domains of this protein. This has already provided some exciting results and these will be pursued. These studies will contribute to an increased understanding of the pathophysiology of falciparum malaria. In the broader sense, our findings in red blood cells (the simplest and best understood of all eukaryotic cells) may be useful in our understanding of the role of proteins in the regulation of cell structure and the mechanical and adhesive properties of eukaryotic cells in general.